[Quota] Lower quota for ephemeral mode (ie. session only)

storage/browser/quota/quota_settings.cc

Index: storage/browser/quota/quota_settings.cc
diff --git a/storage/browser/quota/quota_settings.cc b/storage/browser/quota/quota_settings.cc
index 97daf843933b9d6bb861b010738b96352669b26d..85b5654d5a7684a71c876698a82e4789f2e7965e 100644
--- a/storage/browser/quota/quota_settings.cc
+++ b/storage/browser/quota/quota_settings.cc
@@ -7,6 +7,7 @@
 #include <algorithm>
 
 #include "base/metrics/histogram_macros.h"
+#include "base/rand_util.h"
 #include "base/sys_info.h"
 
 #define UMA_HISTOGRAM_MBYTES(name, sample)                                     \
@@ -15,16 +16,28 @@
 
 namespace storage {
 
+namespace {
+
+// Skews |value| by +/- |percent|.
+int64_t RandomizeByPercent(int64_t value, int percent) {
+  double random_percent = (base::RandDouble() - 0.5) * percent;
+  return value + (value * (random_percent / 50.0));
+}
+
+}  // anon namespace
+
 base::Optional<storage::QuotaSettings> CalculateNominalDynamicSettings(
     const base::FilePath& partition_path,
     bool is_incognito) {
   const int64_t kMBytes = 1024 * 1024;
+  const int k10Percent = 10;

[jsbell, 2017/04/04 16:23:57]

This should probably be named with respect to what it does, e.g.
kRandomizedPercentage

[michaeln, 2017/04/05 01:20:56]

Done.

 
   if (is_incognito) {
     storage::QuotaSettings settings;
-    settings.pool_size =
-        std::min(300 * kMBytes, base::SysInfo::AmountOfPhysicalMemory() / 10);
+    settings.pool_size = std::min(RandomizeByPercent(300 * kMBytes, k10Percent),

[jsbell, 2017/04/04 16:23:57]

Can we make the 300*kMBytes a constant, e.g. kMaxMemoryQuotaMBytes

[michaeln, 2017/04/05 01:20:56]

Done.

+                                  base::SysInfo::AmountOfPhysicalMemory() / 10);

[jsbell, 2017/04/04 16:23:57]

Can we make the 10 here a constant, e.g. kMemoryQuotaDivisor

[michaeln, 2017/04/05 01:20:56]

Done.

     settings.per_host_quota = settings.pool_size / 3;
+    settings.session_only_per_host_quota = settings.per_host_quota;
     settings.refresh_interval = base::TimeDelta::Max();
     return settings;
   }
@@ -81,6 +94,9 @@ base::Optional<storage::QuotaSettings> CalculateNominalDynamicSettings(
   settings.should_remain_available = total * kShouldRemainAvailableRatio;
   settings.must_remain_available = total * kMustRemainAvailableRatio;
   settings.per_host_quota = pool_size / kPerHostTemporaryPortion;
+  settings.session_only_per_host_quota =
+      std::min(RandomizeByPercent(300 * kMBytes, k10Percent),

[cmumford, 2017/04/04 16:38:29]

This doesn't actually do what the title of issue 619927 requests since it
ignores physical memory. If that's desired then how about creating a method,
named something like CalculateEphemeralOriginQuota(), and using it here, and up
above in the incognito section?

[michaeln, 2017/04/05 01:20:56]

I've decoupled them from one another rather than linked them together.

+               settings.per_host_quota / 10);
   settings.refresh_interval = base::TimeDelta::FromSeconds(60);
   return settings;
 }